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fix: do not handle errors during connection #616

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hauleth wants to merge 1 commit into from
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fix: do not handle errors during connection #616

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31 changes: 13 additions & 18 deletions lib/cluster/strategy/postgres.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -52,24 +52,19 @@ defmodule Cluster.Strategy.Postgres do
end

def handle_continue(:connect, state) do
with {:ok, conn} <- Postgrex.start_link(state.meta.opts.()),
{:ok, conn_notif} <- Postgrex.Notifications.start_link(state.meta.opts.()),
{_, _} <- Postgrex.Notifications.listen(conn_notif, state.config[:channel_name]) do
Logger.info(state.topology, "Connected to Postgres database")

meta = %{
state.meta
| conn: conn,
conn_notif: conn_notif,
heartbeat_ref: heartbeat(0)
}

{:noreply, put_in(state.meta, meta)}
else
reason ->
Logger.error(state.topology, "Failed to connect to Postgres: #{inspect(reason)}")
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@chasers chasers Feb 26, 2025

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What happens when this fails loudly does it take down the whole app with it?

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@hauleth hauleth Feb 27, 2025

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I would need to check exactly, but in theory, if the failure happen repeatedly, then it can cause whole application to go down.

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@abc3 abc3 Mar 25, 2025

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does it take down the whole app with it?

No, Supervisor will try to restart the Postgres strategy process, and after exhausting the retries, it will just leave it unstarted. But that change doesn’t make much sense anyway, because the node will be out of the cluster in case of a Postgres failure. You probably want to forward already assigned values, send a connect message after a timeout, and handle them more gracefully

{:noreply, state}
end
{:ok, conn} = Postgrex.start_link(state.meta.opts.())
{:ok, conn_notif} = Postgrex.Notifications.start_link(state.meta.opts.())
{_, _} = Postgrex.Notifications.listen(conn_notif, state.config[:channel_name])
Logger.info(state.topology, "Connected to Postgres database")

meta = %{
state.meta
| conn: conn,
conn_notif: conn_notif,
heartbeat_ref: heartbeat(0)
}

{:noreply, put_in(state.meta, meta)}
end

def handle_info(:heartbeat, state) do
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